Chicago Air Quality in 2020
In 2020, Chicago's air quality (Chicago-Naperville-Elgin, IL-IN-WI area) had a median daily AQI of 60 (Moderate) across 366 monitored days. 24 days (6.6%) reached Unhealthy for Sensitive Groups or worse, 62 were Good, and the year's peak AQI was 197 (Unhealthy). Fine particulate matter (PM2.5) set the daily AQI on 269 of those days. The cleanest month of 2020 was September (median AQI 55, 0 days above 100) and the worst was July (median 74, 11 days above 100, peak 156).
- Good: 16.9%
- Moderate: 76.5%
- Unhealthy for Sensitive Groups: 5.2%
- Unhealthy or worse: 1.4%
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How was Chicago's air quality in 2020?
Moderate on a typical day: median AQI 60, with 24 days above AQI 100 out of 366 monitored — the 4th cleanest of 7 years on record for the area.
- ✓Peak AQI in 2020: 197 (Unhealthy).
- ✓Fine particulate matter (PM2.5) was the main pollutant on 269 days.
- ✓Cleanest month: September; worst: July.
Frequently asked questions
What was the average AQI in Chicago in 2020?▾
EPA's Air Quality System puts Chicago's (Chicago-Naperville-Elgin, IL-IN-WI) median daily AQI for 2020 at 60, which is Moderate. 24 days were Unhealthy for Sensitive Groups or worse and the year's highest AQI was 197.
Which month had the worst air quality in Chicago in 2020?▾
The cleanest month of 2020 was September (median AQI 55, 0 days above 100) and the worst was July (median 74, 11 days above 100, peak 156).
Was 2020 a good or bad year for Chicago's air?▾
Among the 7 years EPA has published for the area (2019–2025), 2020 ranks 4th cleanest by days above AQI 100. 2020's median of 60 is in line with the area's typical annual median of 60.
Chicago month by month in 2020
Chicago air quality month by month, 2020 (Chicago-Naperville-Elgin, IL-IN-WI, EPA AQS daily AQI)
| Month | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| January | 31 | 58 | 0 | 80 | PM2.5 |
| February | 29 | 58 | 0 | 76 | PM2.5 |
| March | 31 | 57 | 0 | 96 | PM2.5 |
| April | 30 | 59 | 0 | 81 | PM2.5 |
| May | 31 | 61 | 0 | 90 | PM2.5 |
| June | 30 | 77 | 8 | 197 | O3 |
| Julyworst | 31 | 74 | 11 | 156 | O3 |
| August | 31 | 63 | 3 | 129 | PM2.5 |
| Septembercleanest | 30 | 55 | 0 | 81 | PM2.5 |
| October | 31 | 56 | 0 | 75 | PM2.5 |
| November | 30 | 61 | 1 | 103 | PM2.5 |
| December | 31 | 62 | 1 | 103 | PM2.5 |
How 2020 compares
Among the 7 years EPA has published for the area (2019–2025), 2020 ranks 4th cleanest by days above AQI 100.
2020's median of 60 is in line with the area's typical annual median of 60.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Chicago
The latest EPA AirNow observation puts Chicago's AQI at 41 (PM2.5). The figures above are multi-year annual statistics, not today's reading.
View current Chicago air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Chicago-Naperville-Elgin, IL-IN-WI), 2019–2025. Daily AQI per CBSA is the highest AQI reported by any monitor in the area that day; the defining parameter is the pollutant that set it. Month and season statistics pool every such day in the period across all years listed. Retrieved 2026-09-09.